(a) Field
The subject matter disclosed generally relates to a turntable. More specifically, the subject matter relates to a vibration-reduced turntable.
(b) Related Prior Art
Turntables are electromechanical systems used to extract musical signals cut as modulations into vinyl or shellac records (a.k.a. discs). As a system, a turntable typically consists of a platter and drive system, a tonearm, and a phono cartridge. The platter provides the rotational energy to the record placed upon it via the platter drive system, energy which the phono cartridge transducer, which is held above the record by the tonearm, needs to trace and to convert the modulations into electrical signals. These electrical signals are then amplified, re-equalized, and finally converted into musical sound-waves by loudspeakers. A key functional requirement of a turntable system is the consistency of the platters rotational velocity, especially when high level modulations, such as, without limitations, loud sounds, typically with low frequency content, provide greater friction to the phono transducer, creating a dynamic load on the platter drive system.
Turntables are extremely sensitive mechanical playback systems, and this makes it essential to reduce all external mechanical and electrical influences as much as possible.
One of the most critical components in any turntable design is the drive mechanism. At first glance, it appears to be a simple task to turn the platter at a constant 33⅓ or 45 RPM. In practice, it is extremely challenging to produce rotational speed that is sufficiently stable to prevent audible degradation of reproduced sound. Close examination of speed stability reveals a host of problems.
Micro speed variations are responsible for audible problems that most audiophiles would not attribute to the turntable drive mechanism. Harshness, muddiness and smearing are the classic symptoms of micro speed variations. In addition problems with a slow, dull presentation can often be traced to deficits in the turntable's drive mechanism.
Human hearing is remarkably sensitive to infinitesimally small errors in the time domain. This has been well documented in digital audio where timing errors (jitter) as small as ten trillionths of a second, have been shown to be detrimental to quality sound reproduction.
Well known prior art documents describe drive systems where a turntable and a motor for driving the turntable are directly coupled. In those systems, a record player is characterized in that a cancellation mechanism is disposed concentrically with the driving motor. The cancellation mechanism performs a reciprocating rotational motion to generate a torque equal in magnitude and reverse in direction with respect to a torque fluctuation developed by rotation of the driving motor. The system thereby cancels the counteractive rotational vibrations exerted on a frame of the record player. However, these systems do not provide an optimized reduction of external mechanical and electrical influences.
There is therefore a need for an improved vibration-reduced turntable allowing an important reduction of the external mechanical and electrical influences.